Artificial ventilation is frequently performed by "first responders" and emergency medical technicians prior to the arrival of advanced life support (paramedics). In order to ventilate properly, the breaths must be given slowly and the volume of gas carefully controlled. It is often difficult to gauge the exact volume and flow-rate of gas delivery. Improper ventilation may cause gas to enter the stomach, which may lead to regurgitation of the stomach contents followed by aspiration of the vomitus into the lungs.
A number of ventilation devices have been reported in the art. However, these devices have all suffered from one or another disadvantage or design defect. For example, in early ventilation devices, it was believed that it was desirable not only to provide a source of ventilating air or gas to resuscitate a patient whose independent inspiration of air or gas is interrupted, but to also provide a suction or vacuum to withdraw air or gas from the lungs. It has since come to be generally accepted in the art that this is not the case. First, damage to the lungs may result from the forced expiration of air or gas, while the natural compliance of the lungs and chest cavity is sufficient to result in expulsion of air or gas even though the patient may not be adequately inhaling on their own. Second, problems of regurgitation of stomach contents have been encountered with these vacuum creating devices with the possible complications of fouling of the device, blockage of air or gas passages with masses of partially digested matter, and aspiration of acidic fluids. Aside from this common misapprehension, a number of prior art devices have also suffered from the inability of a single rescuer to easily operate the device alone. Many prior art devices suffer from inadequate control of the rate or volume of gas delivery. Others are simply cumbersome or awkward to operate. A review of prior art devices of which the applicant is aware follows.
U.S. Pat. No. 1,371,702 (the '702 patent) discloses a respirating device which could introduce and remove gases from the lungs of a patient. The device comprised a large cylinder mounted on a base upon which an operator could place a foot while pumping a piston to provide air or gas to the patient. Because of the closed nature of this system, and the belief that victims would need to have air or gas withdrawn for them, the device of the '702 patent does not provide for unassisted exhalation by the victim. The two hands of the rescuer are not available for making the mask seal on the victim.
U.S. Pat. No. 2,428,451 (the '451 patent) discloses a pressure resuscitator in which a bellows, with a handle attached at the upper end of the bellows, is compressed to deliver air or gas through a face-mask to a victim. The bellows is not contained within any type of rigid cylinder, resulting in difficulty for the rescuer to attain proper vertical alignment of the bellows during depression cycles. In addition, the placement of the handle at the upper end of the bellows means that the operator has but one hand to properly seat the face-mask on the face of a victim. Finally, a complex system of valves is described for achieving proper delivery of fresh air or gas to the victim while still allowing the victim to exhale unassisted.
U.S. Pat. No. 3,461,866 (the '866 patent) discloses a two-cylindered manually operated artificial respirator in which on the downward stroke of a handle, air or gas is supplied to a victim from one cylinder, while on the upward stroke, air or gas is withdrawn from the victim. Rate and volume of air or gas delivery is controlled by the operator limiting the rate and amount of pumping handle travel, with pressure relief valves and audible signals being provided in the event that too much air or gas is being presented to or extracted from the lungs.
U.S. Pat. No. 3,905,362 (the '362 patent) discloses a volume-rate respirator system and method wherein a complex electronic and a vertically movable weight driven system provides precise control of inspiration and expiration rates and volumes. The device of the '362 patent would be expensive, poorly portable, and best adapted for non-emergency maintenance use in a hospital context.
U.S. Pat. No. 3,918,447 (the '447 patent) discloses a ventilator particularly adapted for use on neonates in an incubator wherein a piston within a cylinder divides the cylinder into an upper and a lower chamber. A source of pressurized gas supplied to the upper chamber causes the piston to move downward, thereby forcing air or gas in the lower chamber, which has been supplied from a source of breathing gas, to enter the lungs of the patient. There is no provision for portable use of this device.
U.S. Pat. No. 3,939,830 (the '830 patent) discloses a manually operable dechoking and resuscitating device wherein a handle attached to a piston within a cylinder is biased to move downward to expel air or gas trapped within the cylinder below the piston head. The rate at which the piston moves downward is not readily controllable by the rescuer as the biasing means, a spring, has its own characteristic rate of retraction or expansion. Thus, the rate of air or gas delivery by this device in its ventilation mode is not user controllable. In addition, as the piston is drawn upward for the next downward stroke of air or gas expulsion into the patient, a vacuum is created in the patient's lungs thus possibly causing lung damage, regurgitation, and fouling of the instrument as noted above. In a modified embodiment of the '830 device, the downward-biasing spring is removed and a handle is located on the outside of the cylinder. The handle is located at the upper extremity of the cylinder, as opposed to the placement of a handle close to the bottom of the cylinder in one embodiment of the instant invention. The location of the face mask in the '830 device is at the bottom, center of the cylinder, rather than being eccentrically placed toward the periphery as in one embodiment of the instant invention described below. However, the downward, inhalation cycle of the device is coupled with the upward, exhalation or air or gas extraction cycle of the device in a closed loop, thus preventing unassisted exhalation by the patient. The purpose of the latter embodiment is less to provide ventilation than it is to attempt to cause the lungs to so inflate and deflate as to keep the heart of the patient pumping.
U.S. Pat. No. 4,297,999 (the '999 patent) discloses a portable resuscitation apparatus comprising a rhythm apparatus for indicating the proper sequence or timing of compression and ventilation strokes, a head positioning means to assist in clearing the air or gas passages of the patient, and a mask which will fit most patients. The mask is secured to the patient's face by straps attached to the head positioning means, and air or gas is supplied from an associated remote bellows pump.
U.S. Pat. No. 4,493,614 (the '614 patent) discloses a pump for a portable ventilator. The pump is external to any ventilator apparatus in conjunction with which the pump is used.
U.S. Pat. No. 4,643,719 (the '719 patent) discloses a manually operated, bellows shaped aspirator for removing aspirated matter from the mouth and throat of a victim. Provision of ventilation air or gas is not part of the invention.
U.S. Pat. No. 4,782,831 (the '831 patent) discloses a complex, volume-controlled manual resuscitator. The device involves a system of three communicating chambers, with a balloon in the second chamber. A bulb is used to inflate a balloon to displace gas into the first chamber, thereby delivering to a patient a volume of gas proportional to the volume of gas displaced by the balloon. The third chamber receives ambient air or gas or supplied gas.
U.S. Pat. No. 4,836,198 (the '198 patent) discloses a portable ventilating device wherein a spring mounted in a cylinder opposes the motion of a piston which displaces gas into a patient's lungs. The device may be operated under gas-pressure or manually. However, there is no provision for adjusting the volume of the chamber, and the device thus can only provide a constant volume of gas at a constant rate. Further, it is required that the rescuer open and close external valves to initiate and end cycles.
U.S. Pat. No. 4,898,167 (the '167 patent) discloses an AIDS protection ventilation system comprising a variable volume spring loaded remote bellows pump, operated by the weight of a rescuer, for delivering air or gas to a patient. The remote pump of that system means that while the rescuer is creating a source of air-pressure with one hand remote from the patient, only one hand is available to secure the mask on the victim's face. Even worse, the system relies on a number of insert devices for use with the remote bellows pump the proper operation of which requires the non-pumping hand of the rescuer to time opening and closing of an orifice with a finger.
In a similar fashion to the summary of art found in the Background section of the U.S. Pat. No. 4,898,167 patent, in addition to the distinctions between the instant invention and the prior art devices and the shortcomings in those devices noted above, the following table summarizes some of the differences between some of the features and operation of the foregoing prior art devices and the UVD of the instant invention:
TABLE I ______________________________________ Air or gas expulsion Both bands pressure of rescuer controlled participate in Ancillary internal to creating a rescuer Unassisted Patent device or seal on the activities victim No. remotely? victims face? required? exhalation? Size? ______________________________________ UVD Internal yes no yes small '702 Internal no no no large '451 Internal no yes yes small '866 Extemal no no no large '362 External no yes yes large '447 External N/A N/A yes small '830 Internal no no no small '999 External no no yes small '614 External N/A N/A N/A N/A '719 N/A N/A N/A N/A N/A '831 External no yes yes small '198 External no yes yes small '167 External no yes yes small ______________________________________